Document that wxLogInterposerTemp shouldn't be used

Mark it as deprecated in the documentation without deprecating it
formally in the code, as it seems to be used in some existing code and
there is no urgency to remove it, but using it in new code still doesn't
make any sense.

See wxWidgets#23945.

(cherry picked from commit 543fd3f)

Author: vadz

interface/wx/log.h

@@ -748,13 +748,11 @@ class wxLogInterposer : public wxLogChain
 /**
     @class wxLogInterposerTemp
 
-    A special version of wxLogChain which uses itself as the new log target.
-    It forwards log messages to the previously installed one in addition to
-    processing them itself. Unlike wxLogInterposer, it doesn't delete the old
-    target which means it can be used to temporarily redirect log output.
+    Legacy class which should not be used any longer.
 
-    As per wxLogInterposer, this class must be derived from to implement
-    wxLog::DoLog and/or wxLog::DoLogString methods.
+    @deprecated
+    This class is only preserved for compatibility, but using it can result in
+    unexpected behaviour and memory leaks.
 
     @library{wxbase}
     @category{logging}